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Strategy Habitat: Sagebrush Steppe and Shrublands

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Strategy Habitat: Sagebrush Steppe and Shrublands Habitat: Conservation Summaries for Strategy Habitats Photo © Bruce Taylor Strategy Habitat: Sagebrush Steppe and Shrublands Ecoregions: brush, bitterbrush, and western juniper. There is usually a component Sagebrush steppe and shrublands are a Strategy Habitat in the Blue of bare ground or open sand present. Further from the Columbia River, Mountains, Columbia Plateau, and Northern Basin and Range ecore- big sagebrush steppe communities include basin big sagebrush/needle- gions. Sagebrush habitats also occur in the East Cascades ecoregion. and-thread grass; basin wildrye and bluebunch wheatgrass steppe; and Due to the diversity of sagebrush community types and localized Wyoming sagebrush/bluebunch wheatgrass, which formerly occupied patterns of historic habitat loss, this Conservation Strategy focuses on the low-elevation, loess uplands in the Columbia Plateau. different sage communities for each ecoregion. Blue Mountains: Big sagebrush steppe communities are similar to General Characteristics: those of the Columbia Plateau. Sagebrush shrubland species vary by Sagebrush-dominated communities differ greatly in structure and spe- elevation and soils but include low sagebrush, silver sagebrush, rigid cies composition depending on ecoregion, elevation, soils, moisture sagebrush, basin big sagebrush, Wyoming big sagebrush, mountain big regimes, and fire history. In general, sagebrush habitats occur on dry sagebrush, threetip sagebrush, bitterbrush, and rabbitbrush. Soils vary flats and plains, rolling hills, rocky hill slopes, saddles and ridges where in depth and texture but are non-saline. precipitation is low. Sagebrush steppe is dominated by grasses and forbs (more than 25 percent of the area) with an open shrub layer. In Northern Basin and Range: Big sagebrush habitats include moun- sagebrush steppe, natural fire regimes historically maintained a patchy tain, basin and Wyoming big sagebrush shrublands and shrub steppe. distribution of shrubs and predominance of grasses. In shrub-steppe Structurally, these habitats are composed of medium-tall to tall (1.5 habitats of the Columbia Plateau and Blue Mountains, a soil crust – six feet) shrubs that are widely-spaced with an understory of peren- (called a microbiotic or cryptogrammic crust) composed of lichens, nial bunchgrasses. Basin big sagebrush communities occur on deep mosses, fungi, and bacteria reduces soil erosion and moisture loss. silty or sandy soils along stream channels, in valley bottoms and flats, Sagebrush shrublands are dominated by shrubs, with less area covered or on deeper soil inclusions in low sage or Wyoming big sage stands. by grasses and forbs than in steppe habitats. In many, but not all, Wyoming big sagebrush communities occur on shallower, drier soils. sagebrush shrublands, natural fire regimes created a mosaic of stand Mountain big sagebrush communities occur at montane and subalpine ages and structures. elevations on deep soiled to stony flats, ridges, nearly flat ridge tops, and mountain slopes. The fire frequency in big sagebrush habitats Ecoregional Characteristics: ranges from 10-25 years for mountain big sagebrush and 50-100 years Columbia Plateau: Shrub-steppe habitats are open grass-dominated for Wyoming big sagebrush. communities and are usually found on loamy, wind-deposited (loess) soils. In this ecoregion, shrub-steppe communities can be broadly Although these particular sagebrush communities are considered the divided into two elevational types. Within ten miles of the Columbia priorities for this Conservation Strategy, other sagebrush types also River, sandy shrub-steppe communities occur on unstable, well-drained provide important habitat for wildlife and may need to be considered at soils. These include grasslands dominated by needle-and-thread; shrub- the local and watershed scale or for the conservation of particular spe- steppe habitats dominated by bitterbrush and needle-and-thread grass cies. For example, low sagebrush is important for greater sage-grouse, a or Indian rice grass; and sand dune communities characterized by sage- Strategy Species. 294 Oregon Department of Fish and Wildlife Oregon Conservation Strategy, February 2006 Low sagebrush habitats cover large areas of the Northern Basin and Although Wyoming big sagebrush habitats are still common and Range ecoregion. They are characterized by very shallow, poorly widespread in this ecoregion, they have been altered to some degree developed soils and dominated by low sagebrush, perennial forbs and by unmanaged grazing, invasive species, and altered fire regimes. With Sandberg’s bluegrass. Low sagebrush provides critical wildlife habitat overgrazing and fire suppression, shrub (mostly sagebrush) density for many sagebrush-obligate species. Because of the poor shallow soils increases, bunchgrass and forb density decreases and invasive annual low sagebrush communities are slow (150-300 years) to recover from grasses increase. In many areas, these habitats have shifted from mosa- significant soil disturbance or fire. Soil disturbance in these sites often ics of native perennial grasses, forbs, and shrubs to landscapes heavily result in establishment of invasive annual grasses. dominated by shrubs and invasive annual forbs and grasses. Juniper encroachment is an important issue in mountain big sagebrush com- Conservation Overview: munities between 4,500 and 7,000 feet. Sagebrush habitats in eastern Oregon are both extensive and diverse, ranging from low elevation valleys to high mountain areas and from Big sagebrush habitats have high structural diversity, thus more places grassland-like shrub-steppe to relatively dense shrublands. In addition, to forage, hide, and build nests. As a result, the number of bird species there are many species and subspecies of sagebrush, which are associ- generally increases with sagebrush height. Habitat values are also de- ated with different grasses and herbaceous plants, depending on site pendent on a diverse understory of bunchgrasses and flowering plants. conditions. General ecology and conservation issues vary by sagebrush community type, so conservation actions must be tailored to local Throughout eastern Oregon, loss of grassland-shrub mosaics across conditions and conservation goals. Detailed descriptions of the differ- landscapes and the degradation of understories have contributed to ent sagebrush plant communities are available from sources included the decline of species dependent on high-quality sagebrush habitats. in the references. Also, additional information on sagebrush habitats Strategy Species associated with sagebrush include greater sage-grouse, is in Oregon Department of Fish and Wildlife’s Greater Sage-Grouse ferruginous hawk, loggerhead shrike, sage sparrow, Brewer’s spar- Conservation Assessment and Strategy for Oregon: A Plan to Maintain row, sagebrush lizard, Washington ground squirrel, and pygmy rabbits and Enhance Populations and Habitat. (which often burrow along the interface where low sagebrush mixes with mountain big sagebrush). Other wildlife closely associated with Although sagebrush habitats are still common and widespread in east- sagebrush include black-throated sparrow, sage thrasher, sagebrush ern Oregon, some sagebrush habitat types have high levels of habitat vole, and pronghorn. loss and are of conservation concern. These types vary by ecoregion. In the Blue Mountains, valley-bottom sagebrush types, including threetip Limiting factors to Sagebrush Steppe and Shrubland or basin big sagebrush, that occur on deep soils are particularly at habitats: risk. Also important are the valley margin steppe types with Wyoming Factor: Altered fire regimes and localized issues with prescribed sagebrush, squawapple and bitterbrush. In the lower elevations of the fire: Fire suppression has resulted in undesirable changes in veg- Columbia Plateau, shrub-steppe communities have been almost entirely etation and contributes to increases in the intensity of wildfires. replaced by irrigated agriculture. Remnant habitats occur on public Western junipers encroach into and degrade sagebrush habitats lands such as the Boardman Bombing Range and in scattered patches with fire suppression in some areas. Dense juniper stands are not along roadsides and fields. suitable for species that require open sagebrush habitats. In the Northern Basin and Range, several types of big sagebrush are While a useful tool when tailored to local conditions, prescribed combined into a single priority habitat for this Conservation Strategy, fire is not necessarily suitable for all sagebrush habitat types. Some including mountain, basin and Wyoming big sagebrush shrublands and sagebrush habitats, such as low sagebrush, are extremely slow to shrub steppe. This part of Oregon has some of the largest blocks of recover from disturbance such as prescribed fire. Inappropriately high-quality sagebrush habitat left in the United States, but some types managed fire, both prescribed fire and wildfire, can increase domi- have been impacted by several factors. Basin big sagebrush communi- nance by invasive plants. ties have had the greatest loss as compared to historic distribution. Approach: Carefully evaluate sites to determine if prescribed fire is ap- These communities historically occurred on deep soils, and they have propriate, and be particularly cautious in low productivity needle- been converted to agricultural development in some areas. The deep grass sites where recovery times are prolonged or in sites with soils of basin big sagebrush are important
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